Reconstruction of the population history of Adelie penguin colonies on Ross Island in the high Antarctic using biomarkers suggests that penguin populations boomed during the Little Ice Age, which took place between 1500 and 1800 AD. The findings, published in Scientific Reports this week, differ from results in other more northerly Antarctic regions, suggesting that different responses to climate change may occur at low and high altitudes in the Antarctic.

Penguin population dynamics can be affected by variations in climatic and environmental factors, such as sea-surface temperature, air temperature, snow cover and food abundance. Previous research has indicated that penguin populations in the maritime Antarctic increased when the climate became warmer and decreased when it became cooler. During cold periods, increased sea ice can prevent beach access by penguins to their colonies, and lack of food can also be a problem.

Zhou-Qing Xie and colleagues used biomarkers in sediment collected at Cape Bird on Ross Island to reconstruct population changes in Adelie penguin colonies over the past 700 years. They show that the region transformed from a seal to a penguin habitat at the start of the Little Ice Age when the summer temperature was around 2oC colder than during the previous 200 years, and penguins then became the dominant species. Penguin populations peaked between around 1490 and 1670 AD, the results show. The authors note that extended sea ice can provide abundant krill - a key food source for penguins. They conclude that penguin populations in different altitudes in the Antarctic may undergo different changes in response to climate change.